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1/*
2 * include/linux/idr.h
3 *
4 * 2002-10-18 written by Jim Houston jim.houston@ccur.com
5 * Copyright (C) 2002 by Concurrent Computer Corporation
6 * Distributed under the GNU GPL license version 2.
7 *
8 * Small id to pointer translation service avoiding fixed sized
9 * tables.
10 */
11#include <linux/types.h>
12#include <linux/bitops.h>
13
14#if BITS_PER_LONG == 32
15# define IDR_BITS 5
16# define IDR_FULL 0xfffffffful
17/* We can only use two of the bits in the top level because there is
18 only one possible bit in the top level (5 bits * 7 levels = 35
19 bits, but you only use 31 bits in the id). */
20# define TOP_LEVEL_FULL (IDR_FULL >> 30)
21#elif BITS_PER_LONG == 64
22# define IDR_BITS 6
23# define IDR_FULL 0xfffffffffffffffful
24/* We can only use two of the bits in the top level because there is
25 only one possible bit in the top level (6 bits * 6 levels = 36
26 bits, but you only use 31 bits in the id). */
27# define TOP_LEVEL_FULL (IDR_FULL >> 62)
28#else
29# error "BITS_PER_LONG is not 32 or 64"
30#endif
31
32#define IDR_SIZE (1 << IDR_BITS)
33#define IDR_MASK ((1 << IDR_BITS)-1)
34
35#define MAX_ID_SHIFT (sizeof(int)*8 - 1)
36#define MAX_ID_BIT (1U << MAX_ID_SHIFT)
37#define MAX_ID_MASK (MAX_ID_BIT - 1)
38
39/* Leave the possibility of an incomplete final layer */
40#define MAX_LEVEL (MAX_ID_SHIFT + IDR_BITS - 1) / IDR_BITS
41
42/* Number of id_layer structs to leave in free list */
43#define IDR_FREE_MAX MAX_LEVEL + MAX_LEVEL
44
45struct idr_layer {
46 unsigned long bitmap; /* A zero bit means "space here" */
47 struct idr_layer *ary[1<<IDR_BITS];
48 int count; /* When zero, we can release it */
49};
50
51struct idr {
52 struct idr_layer *top;
53 struct idr_layer *id_free;
54 int layers;
55 int id_free_cnt;
56 spinlock_t lock;
57};
58
59#define IDR_INIT(name) \
60{ \
61 .top = NULL, \
62 .id_free = NULL, \
63 .layers = 0, \
64 .id_free_cnt = 0, \
65 .lock = SPIN_LOCK_UNLOCKED, \
66}
67#define DEFINE_IDR(name) struct idr name = IDR_INIT(name)
68
69/*
70 * This is what we export.
71 */
72
73void *idr_find(struct idr *idp, int id);
74int idr_pre_get(struct idr *idp, unsigned gfp_mask);
75int idr_get_new(struct idr *idp, void *ptr, int *id);
76int idr_get_new_above(struct idr *idp, void *ptr, int starting_id, int *id);
77void idr_remove(struct idr *idp, int id);
78void idr_init(struct idr *idp);